Information generated by data processing systems if often printed in human readable form by any one of several types of highspeed printers. Often these printers are the so-called impact type where the paper being imprinted upon is forced against a platen to form the appropriate characters. Impact printers may contain a font of characters which are selectively forced against the paper to form the desired lines of characters. Another impact printer variety is the matrix printer where wires arranged in a vertical row are selectively projected out of a printhead and forced against the paper. The printhead is moved horizontally along the line being printed and across the paper to print the various characters.
With impact printers, different applications require various numbers of copies. It is common to have a number of sheets of paper interleaved with carbons, so that the appropriate number of copies may be obtained. A ribbon is placed between the printing mechanism (i.e., the printhead in matrix printers) and the first sheet of paper to imprint on the first sheet, while the carbons cause the appropriate markings to be made on the remaining interleaved sheets. In some cases, only one copy is required and, accordingly, no carbons and only one sheet of paper is used.
Since particular applications require various numbers of copies, some means must be provided for adjusting the distance between the printing mechanism and the platen in accordance with the number of sheets being imprinted. That is, if only a single sheet is to be printed, the printing mechanism must be closer to the paper and platen to operate satisfactorily. Conversely, where a larger number of copies are required, the printing mechanism must have its position moved away from the platen.
Several mechanisms have been designed to adjust the position of the printing mechanism with respect to the platen. However, all known prior adjusting mechanisms are difficult to operate and in many cases require partial disassembly of the printing mechanism. Also, the prior mechanisms have been complex, and, consequently, not easily manufacturable and assembled. The present invention overcomes these drawbacks.